Many rotating systems such as phased array antennas aboard ships require liquid cooling for reliable operation. Phased array antennas are large structures and can be attached to an oscillating pedestal normally located on a ship's deck.
Because of their large size, the liquid cooling system for such antennas are located off the rotating pedestal. Typically, fluid coolant passes to and from the rotating antenna at high flow rates and pressures through a relatively narrow space. In military applications, the liquid cooling delivery system must be able to survive high shock loads. Therefore, complex delivery systems consisting of numerous parts are bound to experience more failures than delivery systems with less components. Lighter weight systems with a minimum of performance problems are desired. Additionally, leakage of liquid coolant onto the deck of a ship must be avoided.
Accordingly, because of the lack of space and the various loads involved, pedestal mounted phased array antennas offer unique challenges for the design of the coolant delivery system, especially the dual flow rotating union, also referred to as a liquid rotary joint.
Currently known dual flow rotating unions have a rotating portion, a stationary portion, and at least one port running perpendicular to the rotation axis making packaging of such assemblies difficult. The use of a perpendicular ports also requires larger bearings to withstand the moment loads due to the cantilevered connection to the perpendicular port. Thus, the overall system size and complexity is increased.
Also, currently known dual flow rotating unions that deliver fluid through a rotating axis are large, complex, and heavy units. Moreover, known rotating unions typically utilize a face seal between the fixed and rotating conduits. Face seals, unfortunately, require a large envelope size and thus increase the size of the system. Face seals also require strict tolerances, thus increasing the complexity and cost of the system as well as increasing the potential for system malfunctions or failures. Moreover, face seals do not work well in oscillating applications, such as the phased array antenna system described above.
Furthermore, currently known rotating unions normally require fluid flow through each conduit to be in the same direction for eventual mixing of the fluids, without the capability for delivery and return of the fluids while keeping the fluids in each conduit separate throughout the delivery and return process. In addition, currently known dual flow rotating unions have no provision for leak containment or leak detection at the onset of seal wear or failure.
In summary, no currently available rotating union meets the unique requirements of a phased array antenna system or similar systems.